11.25Scala

案例：统计成绩

1.按行读入文件

import scala.io.Source
//案例：统计成绩

object dd1 {
  def main(args: Array[String]): Unit = {
    //1.按行读入文
    val source = Source.fromFile("score.txt")
    val it = source.getLines()//迭代器
    it.next()//跳过第一行
    while (it.hasNext){
      println(it.next())
    }
    source.close()
  }

}

2.处理数据

    while (it.hasNext){
      val arr = it.next().split("，")
      val name = arr(0)
      val yuwen = arr(1).toDouble
      val shuxue = arr(2).toDouble
      val yingyu = arr(3).toDouble
      val total=yuwen+shuxue+yingyu
      val avg = total / 3

      val s = Student(name,yuwen,shuxue,yingyu,total,avg)
      studentList += s
    }
    source.close()
    //计算单科总分
    var avgyuwen:Double = 0
    var avgshuxue:Double = 0
    var avgyingyu:Double = 0
    studentList.foreach(s=>{
      avgyuwen +=s.yuwen
      avgshuxue +=s.shuxue
      avgyingyu +=s.yingyu
    })
    println("语文平均分",avgyuwen / studentList.length)
    println("数学二平均分",avgshuxue / studentList.length)
    println("英语平均分",avgyingyu / studentList.length)

  }

}

import java.io.PrintWriter
import scala.collection.mutable.ListBuffer
import scala.io.Source
case class Student(name:String,yuwen:Double,shuxue:Double,yingyu:Double,total:Double,avg:Double)
//案例：统计成绩

object dd1 {
  def main(args: Array[String]): Unit = {
    //可变List，保存所有学生数据
    val studentList = ListBuffer[Student]()
    //1.按行读入文
    val source = Source.fromFile("score.txt")
    val it = source.getLines()//迭代器
    it.next()//跳过第一行
    while (it.hasNext){
      val arr = it.next().split("，")
      val name = arr(0)
      val yuwen = arr(1).toDouble
      val shuxue = arr(2).toDouble
      val yingyu = arr(3).toDouble
      val total=yuwen+shuxue+yingyu
      val avg = total / 3

      val s = Student(name,yuwen,shuxue,yingyu,total,avg)
      studentList += s
    }
    source.close()
    //计算单科总分
    var avgyuwen:Double = 0
    var avgshuxue:Double = 0
    var avgyingyu:Double = 0
    studentList.foreach(s=>{
      avgyuwen +=s.yuwen
      avgshuxue +=s.shuxue
      avgyingyu +=s.yingyu
    })
    println("语文平均分",avgyuwen / studentList.length)
    println("数学二平均分",avgshuxue / studentList.length)
    println("英语平均分",avgyingyu / studentList.length)
    //总分的前三名
    //思路：1.对所有的同学总分从高到低来排名
    val list1 = studentList.sortWith((a,b)=>a.total > b.total).slice(0,3)
    println("总分从高到低排名前三")
    list1.foreach(println)
    val list2 = studentList.sortWith((a,b)=>a.yingyu>b.yingyu).slice(0,3)
    println("英语前三名")
    list2.foreach(println)
    val list3 = studentList.sortWith((a, b) => a.shuxue > b.shuxue).slice(0, 3)
    println("数学前三名")
    list3.foreach(println)
    val list4 = studentList.sortWith((a, b) => a.yuwen> b.yuwen).slice(0, 3)
    println("数学前三名")
    list4.foreach(println)
    //写入文件
    val writer = new PrintWriter("统计成绩的结果")//创建一个全面新的文件
    writer.println("姓名，语文，数学，英语，总分，平均分")
    studentList.foreach(s=>{
      val avg = String.format("%.1f",s.avg)//只保留一组有效数字
      writer.println(s"${s.name},${s.yuwen },${s.shuxue},${s.yingyu},${s.total},${avg}")
    })
      writer.println("-"*40)
  
      //总分前三名
      list1.foreach(s=>{
        val avg =String.format("%,1f,s,avg")
        writer.println(s"${s.name},${s.yuwen },${s.shuxue},${s.yingyu},${s.total},${avg}")
      })
    writer.println("-"*40)
    writer.close()

  }

}